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論文

Quantum critical behavior of the hyperkagome magnet Mn$$_3$$CoSi

山内 宏樹; Sari, D. P.*; 安井 幸夫*; 坂倉 輝俊*; 木村 宏之*; 中尾 朗子*; 大原 高志; 本田 孝志*; 樹神 克明; 井川 直樹; et al.

Physical Review Research (Internet), 6(1), p.013144_1 - 013144_9, 2024/02

$$beta$$-Mn-type family alloys Mn$$_3$$$$TX$$ have three-dimensional antiferromagnetic (AFM) corner-shared triangular network. The antiferromagnet Mn$$_3$$RhSi shows magnetic short-range order (SRO) over a wide temperature range of approximately 500 K above the N$'{e}$el temperature $$T_{rm N}$$ = 190 K. Mn$$_3$$CoSi has the smallest lattice parameter and the lowest $$T_{rm N}$$ in the family compounds. The quantum critical point (QCP) from AFM to the quantum paramagnetic state is expected near a cubic lattice parameter of 6.15 $AA. Although $T_N$$ of Mn$$_3$$CoSi is only 140 K, quantum critical behavior is observed in Mn$$_3$$CoSi as the enhancement of the electronic specific heat coefficient $$gamma$$. We study how the magnetic SRO appears in Mn$$_3$$CoSi by using neutron scattering, $$mu$$SR, and physical property measurements. The experimental results show that the neutron scattering intensity of the magnetic SRO does not change much regardless of the suppressed magnetic moment in the long-range magnetic ordered state compared to those of Mn$$_3$$RhSi. The initial asymmetry drop ratio of $$mu$$SR above $$T_{rm N}$$ becomes small, and the magnetic SRO temperature $$T_{SRO}$$ is suppressed to 240 K. The results suggest that the Mn$$_3$$CoSi is close to the QCP in the Mn$$_3$$$$TX$$ system.

論文

Elucidation of solid particle interfacial phenomena in liquid sodium; Magnetic interactions on liquid metal and solid atoms at the solid interface

Tei, C.; 大高 雅彦; 桑原 大介*

Chemical Physics Letters, 829, p.140755_1 - 140755_6, 2023/10

固体金属粒子の界面に付着した液体ナトリウムの核磁気共鳴(NMR)信号を初めて検出することに成功した。本研究では、液体ナトリウムと液体ナトリウム中に浮遊する金属粒子との相互作用の違いによる緩和時間の違いを確認した。その結果、微小チタン粒子表面と液体金属ナトリウムは化学的ではなく物理的に相互作用していることが明らかとなった。

論文

Spontaneous topological Hall effect induced by non-coplanar antiferromagnetic order in intercalated van der Waals materials

高木 寛貴*; 高木 里奈*; 見波 将*; 野本 拓也*; 大石 一城*; 鈴木 通人*; 柳 有起*; 平山 元昭*; Khanh, N.*; 軽部 皓介*; et al.

Nature Physics, 19(7), p.961 - 968, 2023/07

 被引用回数:0 パーセンタイル:95.71(Physics, Multidisciplinary)

In ferromagnets, electric current generally induces a transverse Hall voltage in proportion to the internal magnetization. This effect is frequently used for electrical readout of the spin up and down states. While these properties are usually not expected in antiferromagnets, recent theoretical studies predicted that non-coplanar antiferromagnetic order with finite scalar spin chirality - meaning a solid angle spanned by neighboring spins - can induce a large spontaneous Hall effect even without net magnetization or external magnetic field. This phenomenon, the spontaneous topological Hall effect, can potentially be used for the efficient electrical readout of the antiferromagnetic states, but it has not been experimentally verified due to a lack of appropriate materials hosting such magnetism. Here, we report the discovery of all-in-all-out type non-coplanar antiferromagnetic order in triangular lattice compounds CoTa$$_{3}$$S$$_{6}$$ and CoNb$$_{3}$$S$$_{6}$$. These compounds are reported to host unconventionally large spontaneous Hall effect despite their vanishingly small net magnetization, and our analysis reveals that it can be explained in terms of the topological Hall effect that originates from the fictitious magnetic field associated with scalar spin chirality. These results indicate that the scalar spin chirality mechanism offers a promising route to the realisation of giant spontaneous Hall response even in compensated antiferromagnets, and highlight intercalated van der Waals magnets as a promising quasi-two-dimensional material platform to enable various nontrivial ways of electrical reading and possible writing of non-coplanar antiferromagnetic domains.

論文

Short-range spin order in paramagnetic AgCrSe$$_{2}$$

中村 惇平*; 川北 至信; 岡部 博孝*; Li, B.*; 下村 浩一郎*; 末益 崇*

Journal of Physics and Chemistry of Solids, 175, p.111199_1 - 111199_8, 2023/04

 被引用回数:0 パーセンタイル:17.17(Chemistry, Multidisciplinary)

Muon spin rotation ($$mu$$SR) experiments were performed to directly investigate the temperature dependence of the short-range order or correlations of chromium spins in the paramagnetic phase of AgCrSe$$_{2}$$. The detailed investigation of the $$mu$$SR spectra over a wide temperature range from low to high temperatures revealed that the short-range spin correlations developed below about 184 K. It also confirmed no short-range correlations at high temperatures, which had been controversial in previous quasi-elastic neutron scattering studies. In addition, the muon spin relaxation was qualitatively changed and showed large missing asymmetry below about 89 K, where the correlation clearly implied short-range spin order. There could be a preparative phenomenon of the phase transition or an anisotropic short-range spin correlation.

論文

Ferromagnetic crossover within the ferromagnetic order of U$$_{7}$$Te$$_{12}$$

Opletal, P.; 酒井 宏典; 芳賀 芳範; 常盤 欣文; 山本 悦嗣; 神戸 振作; 徳永 陽

Journal of the Physical Society of Japan, 92(3), p.034704_1 - 034704_5, 2023/03

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

U$$_{7}$$Te$$_{12}$$の単結晶の物理的性質を調べた。U$$_{7}$$Te$$_{12}$$が3つの非等価な結晶ウランサイトを持つ六方晶構造を持つことを確認した。常磁性モーメントは、すべてのサイトで一様なモーメントを仮定すると、ウランサイトあたり約1$$mu_{B}$$と推定される。強磁性相転移は$$T_{rm C}$$=48Kで発生し、面内磁化は急激に増加するが、面外成分はあまり増加しない。磁場冷却条件下で温度がさらに$$T_{rm C}$$以下に低下すると、面外成分はT$$^{star}$$=26K付近で急激に増加する。対照的に、T$$^{star}$$付近で面内成分はほとんど変化しない。比熱測定では、T$$^{star}$$付近に$$lambda$$型の異常がないことが示されているため、これらの振る舞いは、秩序した磁気モーメントの再配向、もしくは複数のウランサイトの連続した逐次磁気転移を示唆している。

論文

Magnetic properties of single crystalline Tb$$_5$$Sb$$_3$$

北折 暁*; 金澤 直也*; 木田 孝則*; 鳴海 康雄*; 萩原 政幸*; 金道 浩一*; 竹内 徹也*; 仲村 愛*; 青木 大*; 芳賀 芳範; et al.

Journal of the Physical Society of Japan, 92(2), p.024702_1 - 024702_6, 2023/02

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

Magnetic properties of Tb$$_5$$Sb$$_3$$ are reported. Unlike previous investigations on a polycrystal showing multiple phase transitions, the present single crystal sample shows a single transition 133 K. It is also shown that the magnetic hysteresis increases at low temperatures.

論文

Development of a miniature electromagnet probe for the measurement of local velocity in heavy liquid metals

有吉 玄; 大林 寛生; 佐々 敏信

Journal of Nuclear Science and Technology, 59(9), p.1071 - 1088, 2022/09

 被引用回数:1 パーセンタイル:33.72(Nuclear Science & Technology)

液体重金属中の局所流速計測において、電磁誘導を用いた計測手法は効果的手法の一つである。永久磁石を利用した流速計として、Ricou and Vives' probeやVon Weissenfluh's probeが広く知られているが、これらの流速計は液温上昇に伴う永久磁石の熱減磁により、流速感度および計測体積が低下することが問題点として挙げられる。特に、永久磁石のキュリー温度を超える温度域では流速検出不能となる。そこで本研究では、流速計が持つ温度依存性の解消を目的とし、小型電磁石を内蔵する流速計を開発した。開発された流速計の直径は6mm、長さは155mmである。流速計の基本性能は、室温環境下における矩形管内水銀流れの局所流速分布計測を通して確認され、流速感度および計測体積が評価された。計測された局所流速分布は数値計算によりその妥当性が確認された。

論文

Single crystal growth and magnetic properties of $$alpha$$-Mn and $$beta$$-Mn

大貫 惇睦*; 青木 大*; 仲村 愛*; 松田 達磨*; 中島 美帆*; 芳賀 芳範; 竹内 徹也*

Journal of the Physical Society of Japan, 91(6), p.065001_1 - 065001_2, 2022/06

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

Single crystals of $$alpha$$-Mn and $$beta$$-Mn are successfully grown. Non-Fermi-liquid relations of the low-temperature resistivity and specific heat are found in the spin-liquid state of $$beta$$-Mn. On the other hand, $$alpha$$-Mn exhibits antiferromagnetic transition.

論文

Experimental analysis on dynamics of liquid molecules adjacent to particles in nanofluids

橋本 俊輔*; 中島 健次; 菊地 龍弥*; 蒲沢 和也*; 柴田 薫; 山田 武*

Journal of Molecular Liquids, 342, p.117580_1 - 117580_8, 2021/11

 被引用回数:3 パーセンタイル:28.4(Chemistry, Physical)

エチレングリコール水溶液中に二酸化ケイ素(SiO$$_{2}$$)ナノ粒子を分散したナノ流体の準弾性中性子散乱測定(QENS)およびパルス磁場勾配核磁気共鳴分析(PFGNMR)を行った。研究目的は、このナノ流体の熱伝導率が理論値を超えて増加するメカニズムを解明することだった。得られた実験結果は、SiO$$_{2}$$ナノ粒子の周りの液体分子の運動が非常に制限されているため、SiO$$_{2}$$ナノ粒子の添加により、エチレングリコール水溶液中の液体分子の自己拡散係数が低下していることを示す。そして温度一定の条件で、SiO$$_{2}$$ナノ流体中で、液体分子の自己拡散係数が減少するにつれて、熱伝導率が増加した。

論文

Probing the long-range structure of the $$T^{+}_{cc}$$ with the strong and electromagnetic decays

Meng, L.*; Wang, G.-J.*; Wang, B.*; Zhu, S.-L.*

Physical Review D, 104(5), p.L051502_1 - L051502_8, 2021/09

 被引用回数:46 パーセンタイル:98.42(Astronomy & Astrophysics)

最近発見された$$T^+_{cc}$$状態の長距離構造をその強い相互作用と電磁相互作用による崩壊の分岐の様子から推定することが可能であることを示した。その結果、$$T_{cc}$$の主成分は$$D^{*+}D^0$$であることがわかった。

論文

Feasibility study of magnetic-domain observation by means of non-resonant magnetic X-ray diffraction

稲見 俊哉*; 菖蒲 敬久; 石井 賢司*

IEEE Transactions on Magnetics, 57(3, Part 2), p.6400105_1 - 6400105_5, 2021/03

 被引用回数:0 パーセンタイル:0(Engineering, Electrical & Electronic)

Although the observation of magnetic domains well below the surface of a sample appears to be relatively easy, in reality, magnetic domains inside metallic samples have not been investigated in detail due to a lack of adequate techniques. Non-resonant magnetic X-ray diffraction (NRMXRD) is a candidate for such 3-D magnetic microscopy. A relatively small focus size of less than 100 nm and a relatively long attenuation length of more than 100 $$mu$$m can be obtained by using high-energy synchrotron X-rays. However, NRMXRD has a disadvantage in that the magnetic contrast is low. It is known that the magnetic contrast in NRMXRD increases with increasing the total polarization of the incident X-rays. In this feasibility study, we carried out NRMXRD experiments on a metallic iron sample to examine whether the magnetic contrast can be sufficiently enhanced even for high-energy X-rays.

論文

Single-crystal growth and magnetic phase diagram of the enantiopure crystal of NdPt$$_2$$B

佐藤 芳樹*; 本多 史憲*; Maurya, A.*; 清水 悠晴*; 仲村 愛*; 本間 佳哉*; Li, D.*; 芳賀 芳範; 青木 大*

Physical Review Materials (Internet), 5(3), p.034411_1 - 034411_9, 2021/03

 被引用回数:1 パーセンタイル:6.65(Materials Science, Multidisciplinary)

Single-crystal growth and magnetic properties of NdPt$$_2$$B are reported on a enantiopure crystal. We observed multiple phase transitions at 9.5 and 11 K under zero magnetic field. Nontrivial magnetic phase diagram demonstrates the competitive interactions in this system.

論文

Spin-orbit-induced Ising ferromagnetism at a van der Waals interface

松岡 秀樹*; Barnes, S. E.*; 家田 淳一; 前川 禎通; Bahramy, M. S.*; Saika, B. K.*; 竹田 幸治; 和達 大樹*; Wang, Y.*; 吉田 訓*; et al.

Nano Letters, 21(4), p.1807 - 1814, 2021/02

 被引用回数:9 パーセンタイル:73.98(Chemistry, Multidisciplinary)

Magnetocrystalline anisotropy, a key ingredient for establishing long-range order in a magnetic material down to the two-dimensional (2D) limit, is generally associated with spin-orbit interaction (SOI) involving a finite orbital angular momentum. Here we report strong out-of-plane magnetic anisotropy without orbital angular momentum, emerging at the interface between two different van der Waals (vdW) materials, an archetypal metallic vdW material NbSe$$_{2}$$ possessing Zeeman-type SOI and an isotropic vdW ferromagnet V$${}_5$$Se$${}_8$$. We found that the Zeeman SOI in NbSe$$_{2}$$ induces robust out-of-plane magnetic anisotropy in V$$_{5}$$Se$$_{8}$$ down to the 2D limit with a more than 2-fold enhancement of the transition temperature. We propose a simple model that takes into account the energy gain in NbSe$$_{2}$$ in contact with a ferromagnet, which naturally explains our observations. Our results demonstrate a conceptually new magnetic proximity effect at the vdW interface, expanding the horizons of emergent phenomena achievable in vdW heterostructures.

論文

Devil's staircase transition of the electronic structures in CeSb

黒田 健太*; 新井 陽介*; Rezaei, N.*; 國定 聡*; 櫻木 俊輔*; Alaei, M.*; 木下 雄斗*; Bareille, C.*; 野口 亮*; 中山 充大*; et al.

Nature Communications (Internet), 11, p.2888_1 - 2888_9, 2020/06

 被引用回数:14 パーセンタイル:74.84(Multidisciplinary Sciences)

Solids with competing interactions often undergo complex phase transitions. Among them, CeSb is the most famous material where a number of the distinct magnetic phases called devil's staircase appear. We observed the electronic structure evolution across the devil's staircase transitions using bulk-sensitive angle-resolved photoemission spectroscopy.

論文

Quasi-one-dimensional magnetic interactions and conduction electrons in EuCu$$_5$$ and EuAu$$_5$$ with the characteristic hexagonal structure

松田 進弥*; 太田 譲二*; 仲井間 憲李*; 伊覇 航*; 郷地 順*; 上床 美也*; 中島 美帆*; 天児 寧*; 本多 史憲*; 青木 大*; et al.

Philosophical Magazine, 100(10), p.1244 - 1257, 2020/04

 被引用回数:3 パーセンタイル:20.21(Materials Science, Multidisciplinary)

Single crystal samples of EuCu$$_5$$ and EuAu$$_5$$ have been successfully prepared. Using those samples, magnetic and electronic anisotropy has been clarified. Magnetic moment in the ferromagnetic state points to the hexagonal $$c$$-axis for both compounds. Electronic anisotropy was found in both electrical resistivity and Fermi surface topology. These anisotropic characteristics are accounted for by the unique hexagonal structure.

論文

Spin glass behavior in EuCu$$_2$$Si$$_2$$ single crystal grown by the flux method

竹内 徹也*; 芳賀 芳範; 谷口 年史*; 伊覇 航*; 安次富 洋介*; 屋良 朝之*; 木田 孝則*; 田原 大夢*; 萩原 政幸*; 中島 美帆*; et al.

Journal of the Physical Society of Japan, 89(3), p.034705_1 - 034705_15, 2020/03

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

Single crystals of EuCu$$_2$$Si$$_2$$ have been grown by the flux method and Bridgman method. The Eu ions of the Bridgman-grown crystal are nearly trivalent and fluctuate depending on the temperature. On the other hand, the Eu ions of flux-grown sample are divalent and thermally stable and show spin-glass behavior at low temperatures. Crystallographic analyses identified random replacement of Cu sites by Si only for the flux-grown samples. Such structural randomness leads to spin-glass features.

論文

Charge radii and electromagnetic moments of $$^{195-211}$$At

Cubiss, J.*; Andreyev, A. N.; 光岡 真一*; 永目 諭一郎; 西尾 勝久; 太田 周也*; 若林 泰生*; 他60名*

Physical Review C, 97(5), p.054327_1 - 054327_19, 2018/05

 被引用回数:30 パーセンタイル:92.76(Physics, Nuclear)

Hyperfine-structure parameters and isotope shifts of $$^{195-211}$$At have been measured for the first time at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy method. The hyperfine structures of isotopes were recorded using a triad of experimental techniques for monitoring the photo-ion current. The Multi-Reflection Time-of-Flight Mass Spectrometer, in connection with a high-resolution electron multiplier, was used as an ion-counting setup for isotopes that either were affected by strong isobaric contamination or possessed a long half-life; the ISOLDE Faraday cups were used for cases with high-intensity beams; and the Windmill decay station was used for short-lived, predominantly $$alpha$$-decaying nuclei. The electromagnetic moments and changes in the mean-square charge radii of the astatine nuclei have been extracted from the measured hyperfine-structure constants and isotope shifts. This was only made possible by dedicated state-of-the-art large-scale atomic computations of the electronic factors and the specific mass shift of atomic transitions in astatine that are needed for these extractions. By comparison with systematics, it was possible to assess the reliability of the results of these calculations and their ascribed uncertainties. A strong deviation in the ground-state mean-square charge radii of the lightest astatine isotopes, from the trend of the (spherical) lead isotopes, is interpreted as the result of an onset of deformation. This behavior bears a resemblance to the deviation observed in the isotonic polonium isotopes. Cases for shape coexistence have been identified in $$^{197,199}$$At, for which a significant difference in the charge radii for ground (9/2$$^{-}$$) and isomeric (1/2$$^{+}$$) states has been observed.

論文

Crystallographic, magnetic, thermal, and electric transport properties in UPtIn single crystal

松本 裕司*; 芳賀 芳範; 立岩 尚之; 山本 悦嗣; Fisk, Z.*

Journal of the Physical Society of Japan, 87(2), p.024706_1 - 024706_4, 2018/02

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

Single crystal samples of UPtIn with the hexagonal structure are grown from indium flux. Strong uniaxial magnetic anisotropy is revealed from magnetic property measurements. Specific heat measurement reveals a significant deviation from $$T$$-linear behavior, indicating the smaller electronic specific heat than the previous study.

論文

Measurement of thermal deformation of magnetic alloy cores of radio frequency cavities in 3-GeV rapid-cycling synchrotron of Japan Proton Accelerator Research Complex

島田 太平; 野村 昌弘; 田村 文彦; 山本 昌亘; 杉山 泰之*; 大森 千広*; 長谷川 豪志*; 原 圭吾*; 吉井 正人*

Nuclear Instruments and Methods in Physics Research A, 875, p.92 - 103, 2017/12

 被引用回数:0 パーセンタイル:0.02(Instruments & Instrumentation)

Magnetic alloy cores loaded in radio frequency cavities are employed to achieve a high field gradient in the 3-GeV Rapid-Cycling Synchrotron of the Japan Proton Accelerator Research Complex. We use three core-types, which were manufactured in three different processes. Buckling occurred in some cores of only one of the three core types. In order to find out the mechanism of buckling, we measured thermal deformations of the two core types, which had not buckled and the core types, which had buckled, while changing their temperatures by RF heating in air. Furthermore, we calculated the thermal stress using the results of the experiments. These experiments yielded that there was no remarkable difference in the strength of thermal stress between the core types, which had not buckled, and the core types, which had buckled; however, that there was a clear difference in the behavior of thermal deformations. The local deformations appeared, when a certain temperature was exceeded, and accelerated with temperature rise in the buckled core types. This was not seen with core types that didn't show the buckling problem. We conclude that the repetition of these catastrophic and local deformations, which are accelerated with the temperature rises, lead to the buckling. This result contributes to the stable operation of RCS.

論文

Experimental observation of temperature and magnetic-field evolution of the 4${it f}$ states in CeFe$$_{2}$$ revealed by soft X-ray magnetic circular dichroism

斎藤 祐児; 保井 晃*; 渕本 寛人*; 中谷 泰博*; 藤原 秀紀*; 今田 真*; 鳴海 康雄*; 金道 浩一*; 高橋 稔*; 海老原 孝雄*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07

AA2017-0611.pdf:0.36MB

 被引用回数:2 パーセンタイル:17.22(Materials Science, Multidisciplinary)

単結晶CeFe$$_2$$を用い、X線吸収(XAS)磁気円2色性(XMCD)の高精度実験により、その強磁性的秩序相におけるCe4$$f$$状態を調べた。Ce $$M_{4,5}$$ XMCDスペクトルは、温度及び磁場に依存した形状変化を示す一方、Ce $$M_{4,5}$$ XAS、Fe $$L_{2,3}$$ XAS及びXMCDスペクトルでは変化が観測されないという通常の強磁性体とは異なる現象が観測された。このような振る舞いは、Ce 4$$f^1$$配置の$$J=5/2$$基底状態と$$J=7/2$$状態が混ざり合ったことに由来すると解釈できる。外部摂動に対し非常に敏感なCe 4$$f$$状態は、本物質での強磁性相と反強磁相が隣接する磁気不安定性と関連付けることができる。我々の実験データは、混成の強い強磁性Ce化合物の物性に対して、貴重な情報を与える。

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